Fix the problem of memory leak in gradient pixmap
generating. The problem caused by we do not call
glDeleteShader when destroy a shader program. This patch
will split the gradient pixmap generating to three
category. If nstops < 6, we will use the no array version
of the shader, which has the best performance. Else if
nstops < 16, we use array version of the shader, which is
compiled and linked at screen init stage. Else if nstops >
16, we dynamically create a new shader program, and this
program will be cached until bigger nstops.
Signed-off-by: Zhigang Gong <zhigang.gong@linux.intel.com>
3d96929596